The Greenland ice sheet melted at a record rate this year, the largest ever since satellite measurements began in 1979, a top climate scientist reported on Monday.“The amount of ice lost by Greenland over the last year is the equivalent of two times all the ice in the Alps, or a layer of water more than one-half mile deep covering Washington DC,” said Konrad Steffen of the University of Colorado at Boulder.

Greenland is about one-fourth the size of the United States and about 80 percent of it is covered by the ice sheet. One-twentieth of the world’s ice is in Greenland; if it all melted it would be equivalent to a 21-foot (6.4 meter) global sea level rise, the scientists said.

- Reuters, Dec 10 2007

Doomsday tourism, eh? Nice term. It’s a fine difference to eco-tourism, where you just want to see natural sites. Here, you want to see natural sites that is not predicted to remain for long. 

An interesting story about the eco-tourist boom of those rushing to see sites that are changing so fast they may disappear and never be seen as they were. Most of these are ice disappearing in one form or another, or sea levels rising. Let’s hope those who are rushing there are doing so responsibly so these sites are not gone sooner than would be otherwise without their presence!

Antarctica: the Müller ice shelf and the Larsen ice shelf are shrinking dramatically.

Mt Kilimanjaro, Tanzania: global warming is blamed for melting of the year-round snows at the summit of Africa’s highest mountain. They could be gone in 15 years.

The Arctic ice cap: the melting of icebergs and ice caps in the Arctic is blamed on global warming and threatens the habitats of species such as polar bears.

The Maldives: rising sea levels (3½in per year) could make these 1,200 islands in the Indian Ocean uninhabitable within 100 years.

Venice: the Italian city is sinking into the Adriatic and rising sea levels could make things worse.

Alaska: American travel agents report thousands heading for the shrinking glaciers and melting permafrost.

Great Barrier Reef, Australia: it’s been predicted that rising water temperatures, which are bleaching the famously vivid reefs, will kill 95 per cent of the living coral by 2050.

Kitzbuhel, Austria: the home of the world’s most fearsome ski run is among low-lying Alpine ski resorts whose long-term futures are threatened by rising temperatures - on average the warmest they have been for 1,250 years.

Galapagos Islands: rising water temperatures are bleaching coral and causing the deaths of marine species.

Patagonia: South American glaciers are also retreating.

According to the International Association of Antarctic Tour Operators, more than 37,000 tourists visited the continent last year - double the number five years ago. A third came from America, while the second largest contingent - one in seven visitors - travelled from Britain. “There definitely is a rush to see and explore the world before it changes,” said Matt Kareus, of Natural Habitat, which operates excursions to Antarctica.

Interesting. We Canadians flock to warmer weather. Going to Antartica isn’t exactly our style, though, mind you, I personally took a half day vacation last winter to photograph Halifax harbour freezing in -36C windchill. We’ve got the deepest ice free unfrozen natural harbour in the world, in case you didn’t know. Besides, we Canadians have got the North Pole so why go to the South Pole?

At least we’ve got the North Pole for now.

Merry Christmas again! [Envirostats author]

- Eco-tourism story via The Telegraph, Dec 23 2007

Some experts are describing as this to be the last big carve-up of territory in history.

If you want to turn this into a more traditional statistic, just do the math for a countdown of number of days until May 13 2009. I don’t know how to do that with a blog entry.

The source article talked about British, Chilean and Argentinean claims, among others, to Antarctica.

- Reuters, Oct 18 2007

Perennial ice is ice more than 1 year old. Single-year ice is typically less than 5 feet thick; 2-3 year old ice averages 6½ feet thick; and ice 10 years or older averages more than 16 feet thick; so perennial ice averages somewhere between 6½ and 16½ feet. The ice cover typically loses 5 feet of thickness during the summer melt season, April through September. Note though, that this measure of perennial ice is by volume, not area covered, because area covered has generally remained the same, but an increased amount of older, thicker perennial sea ice was swept by winds out of the Arctic Ocean into the Greenland Sea.

The article was about how the environmental impact on this ice may be the key to predicting how much the Arctic ice will melt each summer, which has become a topic of environmental interest this past summer from record breaking Arctic ice melting as shown in Stat 0368. An proven indicator has yet to be discovered but you can judge some data for yourself.

The total square miles of ice has remained the same, but the perennial ice has decreased by 0.42 million square miles (1.1 million square km), which was the 23% reduction in the headline statistic.

It was not clear in the article but it would seem to me that perennial ice lasts because it is more resistant melting to newer ice for whatever reasons, like being packed in. Having a large, stable volume of this ice prevents temperatures from changing more rapidly and therefore melting other newer ice. Ice older than 10 years could also be theorized to influence resistance to temperature situations, but it does not seem it is exposed enough to do so and there is no correlation in the data.

The tendency for predictions is to look at past data and extrapolate. Linear extrapolations is often done whereby the “line” (that is sometimes a unidirection curve) is simply allowed to continue. A lot of times, this proves to be a rather bad call, especially with something that can be as complex as atmospheric science. Even extrapolations to best fitting curves to data can often be inaccurate because the situations tend to be far more complex than a one dominant variable behaviour. However, prediction due to causality is difficult so it is not done as often, possibly due to lack of data to match for causality. In some ways, extrapolation by causality is just as big a risk as linear extrapolation, but if the data were there like in this case, it may not be as inaccurate as simpler models. The source study was innovative for that reason, looking for another variable to the one seen in area of ice coverage and correlating it to observations of parallel data in the perennial ice of the total ocean ice. I also feel it is likely to be more correct than previous hypotheses. [Envirostats author]

Here are some other statistics on steely perennial sea ice:

• The average age of perennial ice was more than 10 years prior to 1989. More recently the average age is 3 years.
• There have been instances in which ice has been known to survive 30 years or more. An ice station known as T-3, for instance, was abandoned in 1954 but the remains continued to be sighted for 30 years.
• Perennial ice averages 6 ½ to 16 ½ feet in thickness.
• Powerful winds and ocean circulation can force places where the ice is even thicker because of ridging and rafting. The ridges can tower over the surface of the ice, while below, keels of ice as long as 40 feet can jut into the ocean.
• The coastline of Canada’s arctic archipelago near Greenland is an area with so much of this ridging and rafting that icebreakers take care to skirt the area.

The same wind and ocean circulation that shoves ice in thick layers against Canada’s arctic archipelago also propels ice just as forcefully out Fram Strait along Greenland’s eastern shore. The ice eventually melts in the Atlantic Ocean. Winds the last two years, powered by the Arctic Oscillation, were particularly strong and swept out more ice than usual, something that also happened in the early 1990s.

- Ignatius Rigor of the University of Washington’s Applied Physics Laboratory and Son Nghiem of NASA’s Jet Propulsion Laboratory, via the Environmental News Network, Oct 4 2007

Some cautious good news for a change! 

Each year, the ozone hole comes and goes, persisting till November or December, unlike popular belief that it is a permanent large hole. Ozone is then lost as temperature and atmospheric conditions change, forming the hole until conditions change again. The loss, though, has huge climatic impacts and could be cumulative so this isn’t a “temporary” problem just because the hole more or less disappears for a while in November or December, and at some point, if the ozone hole grows large enough, it will not entirely disappear and then we’ll really be looking at trouble because of what may happen if it ever reaches that stage. This understanding of the coming and going of the ozone hole will allow this article to make much more sense since it talks about loss of ozone and ozone hole size being of the same proportions, which could only be if they had a common zero point, when the hole would not exist.

So in Nov or Dec 2005, the ozone hole regenerated, only to lose 40 million tonnes in 2006, then regenerated again, and lose 27.7 million tonnes in 2007, but recovering again which is why the source can quote the 2007 loss already before year’s end. The 30% reduction in ozone volume loss is the same as the 30% reduction in hole size because both were measured relative to the same zero value. Other selected scientific information follow from the source article. [Envirostats author]

Ozone loss is derived by measuring the area and the depth of the ozone hole. The area of this year’s ozone hole – where the ozone measures less than 220 Dobson Units – is 24.7 million sq km, roughly the size of North America, and the minimum value of the ozone layer is around 120 Dobson Units.

A Dobson Unit is a unit of measurement that describes the thickness of the ozone layer in a column directly above the location being measured. For instance, if an ozone column of 300 Dobson Units is compressed to 0º C and 1 atmosphere (the pressure at the Earth’s surface) and spread out evenly over the area, it would form a slab of ozone approximately 3mm thick.

Scientists say this year’s smaller hole – a thinning in the ozone layer over the South Pole – is due to natural variations in temperature and atmospheric dynamics (illustrated in the time series in the picture below) and is not indicative of a long-term trend.

Ozone hole over Antarctica measured in September 2007 by Envisat. The ozone loss in 2007 peaked at 27.7 million tonnes, compared to the 2006 record ozone loss of 40 million tonnes. (Credit: KNMI - ESA)

“Although the hole is somewhat smaller than usual, we cannot conclude from this that the ozone layer is recovering already,” Ronald van der A, a senior project scientist at Royal Dutch Meteorological Institute (KNMI), said.

“This year’s ozone hole was less centred on the South Pole as in other years, which allowed it to mix with warmer air, reducing the growth of the hole because ozone is depleted at temperatures less than -78 degrees Celsius.”

During the southern hemisphere winter, the atmospheric mass above the Antarctic continent is kept cut off from exchanges with mid-latitude air by prevailing winds known as the polar vortex. This leads to very low temperatures, and in the cold and continuous darkness of this season, polar stratospheric clouds are formed that contain chlorine.

As the polar spring arrives, the combination of returning sunlight and the presence of polar stratospheric clouds leads to splitting of chlorine compounds into highly ozone-reactive radicals that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.

The ozone hole, first recognised in 1985, typically persists until November or December, when the winds surrounding the South Pole (polar vortex) weaken, and ozone-poor air inside the vortex is mixed with ozone-rich air outside it.

Ozone is a protective layer found about 25 km above us mostly in the stratospheric stratum of the atmosphere that acts as a sunlight filter shielding life on Earth from harmful ultraviolet rays. Over the last decade the ozone layer has thinned by about 0.3% per year on a global scale, increasing the risk of skin cancer, cataracts and harm to marine life.

The thinning of the ozone is caused by the presence of ozone destructing gases in the atmosphere such as chlorine and bromine, originating from man-made products like chlorofluorocarbons (CFCs), which have still not vanished from the air but are on the decline as they are banned under the Montreal Protocol, which was signed on 16 September 1987.

- The European Space Agency (ESA), from which data was obtained from its satellites, via Science Daily, Oct 4 2007